Formulation and evaluation of an implantable polymeric configuration for application in AIDS Dementia Complex

Abstract:

Drug delivery to the brain has challenged medical professionals for several decades, with 98% of small molecules and 100% of large molecules unable to cross the blood brain barrier (BBB). Biocompatible, biodegradable polymers have been extensively researched for the oral delivery of therapeutic agents, but to date has not been successfully manipulated for the formulation of an implantable device. We have therefore utilised such polymers for the formulation and design of an implantable nanoenabled multipolymeric drug delivery device (NMDDD) for the management of AIDS Dementia Complex (ADC).
ADC is a central nervous system (CNS) complication of HIV, associated with a host of debilitating cognitive, motor and behavioural symptoms. ADC remains a serious manifestation of HIV/AIDS in both developing and developed countries, affecting both adults and children, with death expected within 6 months of initial diagnosis. Zidovudine (AZT), the current gold standard for the management of ADC, has demonstrated the best penetration into the CNS. It is capable of reducing viral replication in the CNS and managing neurological abnormalities associated with ADC, with clinical efficacy evidenced by the decline in morbidity and mortality of patients treated with this drug.
Nanotechnology, an interdisciplinary field of research, involving the manipulation of matter on a submicron level, is receiving emerging interest for the formulation of novel drug delivery systems. As they can potentially be manipulated to react in a bioresponsive manner, nanopharmaceuticals have received much attention for site-specific drug delivery and were therefore employed in the formulation of an implantable NMDDD, with AZT employed as the model drug, for the management of ADC.
Nanoparticles were prepared by means of an approach utilising controlled gelation of alginate, employing cationic crosslinking of the anionic alginate to precipitate nanoparticles. A 3-factor Box-Behnken statistical design was employed for the optimisation of nanoparticle and multipolymeric scaffold formulations. Nanoparticles measuring 68.04nm (SD<0.0002) in size with a zeta potential of -13.4mV (SD<0.0005) were formulated. Nanoparticles presented with a mean dissolution time (MDT) of 46.046 hours 30 days post exposure to phosphate buffered saline (PBS), pH 7.4. In an attempt to further retard drug release and to formulate a device for implantation in the frontal lobe of the brain, nanoparticles were dispersed within a robust multipolymeric matrix. Matrix erosion was calculated at 28%w/w (SD<0.001) for multipolymeric scaffold and a matrix resilience of 4.451%w/w (SD<0.007) was observed 30 days post exposure to PBS, indicating slow degradation of the NMDDD. MDT was reduced to 12.570 hours (SD<0.0005) with dispersion of the nanoparticles within a polymer matrix, supporting the application of the drug-loaded MDDD in the management of ADC patients.
The optimised multipolymeric nanoparticulate scaffold was implanted into the frontal lobe of the rat brain, for investigation of drug release characteristics and tissue response to the device following in vivo administration.